Fat cells or adipocytes play a central role in obesity, diabetes, and metabolic disease. White adipocytes store excess energy in the form of triglycerol, and brown adipocytes dissipate chemical energy into heat. In addition to these bioenergetics functions, adipocytes also have important endocrine functions. While several adipocyte-derived secreted factors, or adipokines, have been shown to have important physiological roles, bioinformatic analyses suggest that adipocytes may secrete more than 1,000 unique polypeptides. The vast majority of these gene products remain uncharacterized, representing a major opportunity for discovering new biology with translational potential. To that end, we have employed chemical and genetic tools to label and enrich circulating proteins in a cell-selective manner. Using bio-orthogonal non-canonical amino acid tagging (BONCAT) along with mass spectrometry we have characterized the secretome of white, brown, and beige adipocytes. We have identified more than 800 unique proteins, with approximately 300 showing fat cell type specific enrichment. Our studies have focused on a brown and beige fat specific protein encoded by a previously uncharacterized open reading frame (BAT-ORF). The mRNA encoding this protein is expressed in UCP1+thermogenic adipocytes, induced by cold and repressed by warm temperature, and upregulated following thiazolidinedione treatment. We have found that the BAT-ORF gene encodes two isoforms, only one of which is secreted. We have generated mice with genetic deletion of each isoform using CRISPR-Cas9. Preliminary data suggests these mice have decreased energy expenditure. Complete characterization of these mice is underway and data will be presented. We will also present a method using genetically engineered mouse models that allows us to specifically label and enrich secreted proteins in the blood in a cell-type specific fashion.
C.J. Choi: None. A.A. Crane: None. P. Cohen: None.
American Diabetes Association/Pathway to Stop Diabetes (1-17-ACE-17 to P.C.)